Problem: $-\dfrac{2}{3} - \dfrac{4}{10} = {?}$
Solution: $ = - {\dfrac{2 \times 10}{3 \times 10}} - {\dfrac{4 \times 3}{10 \times 3}} $ $ = - {\dfrac{20}{30}} - {\dfrac{12}{30}} $ $ = - \dfrac{{20} - {12}}{30} $ $ = -\dfrac{32}{30}$